As requested I am adding a temporary answer.
This error
Error: Command \FA already defined
It affects some calls to fontawesome
either direct or in a similar fashion to those reported in xparse/command-already-defined
The solution is to update all secondary calls of
\newfontfamily{\FA}{FontAwesome}
to be \setfontfamily{\FA}{FontAwesome}
.
Is a current known open issue #234 (2018/2019) in awsome cv due to above need to change the .cls
syntax and should have been closed by downloading the latest version. However the fix does not appear to have been Pull Requested or added to the master .cls
file.
The working modified awesome-cv.cls
from last year is available here
Note at the same time you need to ensure the fonts are in the correct /fonts subfolder to the cv, resume and cover-letter! that is in the folder with the tex files the fonts folder should be a sub folder /awsometex/fonts/fontfiles where awsometex is the folder with letter.tex etc and the fontfiles are those from the package.